Programme Lagging and saving takes forever

[TheColdEditor]

I have been using Premiere Pro for a few weeks now with no problem but for the last 2 weeks the videos played in the software are lagging badly. I can still edited them but it is getting harder to do because of the lag. Also the last few days the time of saving an edit video takes a lot longer then before. A 20 minute video takes over 2 hours, 2 weeks ago that would be done within 20 minutes maybe. 

I already tried a bunch of things out and even set my PC back to factory settings but the problem with the programme stays. Anybody any idea why after weeks of using it with no problem suddenly this all happens? I really like to know because I paid a buttload of money for a programme that I do not using anymore after only a few weeks.